1. Field of the Invention
The present invention relates to cyclic phenolic thioethers and more particularly relates to the novel compounds of Formula I which are 5-lipoxygenase inhibitors. The compounds of Formula I are useful, for example, as anti-inflammatory and anti-allergy agents and in the treatment of hypersensitivity reactions, psoriasis, asthma, and related disorders and conditions in which physiologically active agents formed in the 5-lipoxygenase metabolic pathway are involved. Compounds of the present invention may be useful in treating arthritis, asthma, and psoriasis. Some compounds of the present invention also stimulate superoxide generation and may be useful as adjunctive therapeutic agents in the treatment of infections. Other compounds of the present invention inhibit superoxide generation and may be useful in the therapeutic or prophylactic treatment of disease conditions which are mediated wholly or partly by superoxide generation such as adult respiratory distress syndrome, superoxide mediated inflammatory or allergic conditions, and other medical conditions which are caused by or aggravated by superoxide.
2. Background Information
It is well recognized that arachidonic acid, an essential unsaturated fatty acid, is enzymatically oxygenated to various products, including, prostaglandins, thromboxanes, the 5-, 11-, 12- and 15-hydroxyeicosatetraenoic acids (HETEs, DIHETEs) and hydroperoxyeicosatetraenoic acids (HPETEs) and the leukotrienes, all of which have potent physiological effects. The leukotrienes, which are produced via the 5-lipoxygenase pathway, are the major contributors to the onset of the symptoms of asthma, and mediators for immediate hypersensitivity reactions, inflammation and other allergic responses.
Leukotrienes are found in inflammatory exudates and are involved in the process of cellular invasion during inflammation. The term "leukotrienes" is used as a generic term to describe a class of substances, such as slow-reacting substance (SRS) which is an important mediator in asthma and other hypersensitivity reactions. Immunologically generated SRS is usually referred to as slow-reacting substance of anaphylaxis (SRS-A). SRS-A consists of leukotrienes (LT) known as A.sub.4, B.sub.4, C.sub.4, D.sub.4, and E.sub.4. LTC.sub.4 is at least 100 times more potent than histamine in causing long lasting bronchoconstricting effects. The leukotrienes also increase vascular permeability and cause decreased cardiac output and impaired ventricular contraction. LTB.sub.4 may be an important mediator of inflammation in, for example, inflammatory bowel disease.
Chemotaxis is a reaction by which the direction of migration of cells is determined by substances in their environment. It is one of the major processes bringing leukocytes from the blood to an inflammatory site, whether the inflammation is caused by an infectious agent, allergic challenge, or other pro-inflammatory stimuli. LTB.sub.4 is not only chemotactic for neutrophils and monocytes, but is also highly active in stimulating eosinophil locomotion. LTB.sub.4 also stimulates calcium influx and aggregation of polymorphonuclear leukocytes and LTB.sub.4 may, thus, play an important role in mediating both acute and chronic inflammation.
Rheumatoid spondylitis is characterized by an acute neutrophil flareup in the joint which is associated with elevated levels of LTB.sub.4. LTB.sub.4 is also present in gouty effusions; and exposure to urate crystals is known to stimulate LTB.sub.4 production by neutrophils. Accordingly, the 5-lipoxygenase inhibitors of the present invention through inhibition of neutrophil attraction and activation in arthritic joints should reduce the protease and oxidative burden believed responsible for joint destruction in arthritic diseases.
Aspirin and the other non-steroidal anti-inflammatory agents (NSAIDs) such as indomethacin, ibuprofen, fenoprofen, and the like, inhibit the synthesis of prostaglandins via the cyclooxygenase pathway of arachidonic acid metabolism. These prostaglandin synthetase inhibitors generally exhibit anti-inflammatory, anti-pyretic and analgesic activity, and are widely used in the treatment of arthritis. The non-steroidal anti-inflammatory agents can lead to the formation of additional pro-inflammatory derivatives of arachidonic acid produced through the 5-lipoxygenase pathway which play a role in immediate hypersensitivity reactions and also have pronounced inflammatory effects. Administration of the NSAIDs alone can produce allergic reactions including bronchospastic reactivity; skin rashes; syndrome of abdominal pain, fever, chills, nausea and vomiting; and anaphylaxis. For this reason, aspirin and the other non-steroidal anti-inflammatory agents (NSAIDs) are generally contraindicated for patients suffering from asthma or who have previously exhibited allergic sensitivity to aspirin or other NSAIDs.
Prior to the recognition of the significance of the 5-lipoxygenase pathway of arachidonic acid metabolism in allergic reactions and inflammation, the search for effective therapeutic agents was based primarily on those agents which treated the symptoms of allergy and inflammation. There has since been an effort to develop new drugs which selectively block the formation of the mediators of these conditions, and the present invention provides new chemical entities which are inhibitors of the 5-lipoxygenase pathway and are useful in the treatment of asthma, rheumatoid arthritis, psoriasis, and other allergic, hypersensitivity, and inflammatory conditions.
The present invention provides compounds which block the 5-lipoxygenase metabolic pathway and, therefore, block the formation of the leukotrienes responsible for allergy and inflammation, and represent therapeutic agents which are useful in the treatment of allergic and hypersensitivity reactions and inflammation, alone, or also may be utilized in combination with other lipoxygenase inhibitors or with cyclooxygenase inhibitors such as the non-steroidal anti-inflammatory agents.
Recently, oxygen radicals have been implicated in the pathogenesis of many diseases. This implication is reflected by the many conferences devoted to this topic, books on the subject of free radicals and disease, and the appearance of two new specialized journals: Free Radical Research Communications, and Free Radical Biology and Medicine.
Much is known about the physicochemical properties of the various oxygen radicals, but knowledge of their overall importance in the initiation and amplification of human disease is limited. Some clinical conditions in which oxygen radicals are thought to be involved are discussed in Cross, C. E., et al., "Oxygen Radicals and Human Disease," ANN. INT. MED., 107:526-545 (1987) (see Table 1, p. 527) and Ward, P. A., et al., "Oxygen Radicals, Inflammation, and Tissue Injury," FREE RADICAL BIOLOGY & MEDICINE, 5:403-408 (1988). Among the clinical conditions in which oxygen radicals are thought to be involved are, for example, inflammatory-immune injury, autoimmune diseases, ischemia-reflow states, aging disorders, cancer, cigarette-smoke effects, emphysema, acute respiratory distress syndrome (ARDS), atherosclerosis, rheumatoid arthritis, senile dementia, cataractogenesis, retinopathy of prematurity, radiation injury and contact dermatitis.
Oxygen radicals are capable of reversibly or irreversibly damaging compounds of all biochemical classes, including nucleic acids, protein and free amino acids, lipids and lipoproteins, carbohydrates, and connective tissue macromolecules. These species may have an impact on such cell activities as membrane function, metabolism, and gene expression. Oxygen radicals are formed in tissues by many processes (see Cross, et al., p. 528, Table 2). These are believed to be both endogenous, such as mitochondrial, microsomal and chloroplast electron transport chains; oxidant enzymes such as xanthine oxidase, indoleamine dioxygenase, tryptophan dioxygenase, galactose oxidase, cyclooxygenase, lipoxygenase, and monoamine oxidase; phagocytic cells such as neutrophils, monocytes and macrophages, eosinophils, and endothelial cells; and antioxidation reactions; and exogenous, such as redox-cycling substances, drug oxidations, cigarette smoke, ionizing radiation, sunlight, heat shock and substances that oxidize glutathione. They may be involved in the action of toxins such as paraquat, cigarette smoke, and quinone antitumor drugs.
Those compounds of the present invention which inhibit superoxide generation may be useful in the treatment of diseases mediated by superoxide generation.
There are also some conditions in which the generation of superoxide may be desirable. Those compounds of the present invention which stimulate superoxide generation may be useful in the adjunctive therapy of microbial infections. See Goodman and Gilman's, The Pharmacological Basis of Therapeutics (7th Edition, 1985) p. 660-673; P. A. Ward, et. al., "Oxygen Radicals, Inflammation and Tissue Injury, " FREE RADICAL BIOLOGY & MEDICINE, 5: 403-408 (1988); and C. E. Cross, et. al., "Oxygen Radicals and Human Disease, "; ANN. INT. MED., 107: 526-545 (1987). Generation of reactive oxygen species is a critical event in successful host defense against invading organisms. Both neutrophils and macrophages rely on a variety of oxidants to damage bacterial constituents (see V. L. Shepherd, "The role of the respiratory burst of phagocytes in host defense," SEMIN. RESPIR. INFECT. (United States) Jun. 1986, 1 (2) p. 99-106.
Various thioether compounds have been described previously. For example, U.S. Pat. No. 4,711,903 and its continuation-in-part, U.S. Pat. No. 4,755,524 disclose compounds of the formula ##STR2## wherein: R.sub.1 and R.sub.2 are the same or different and independently represent tert-alkyl or phenyl; A represents methylene or methylene substituted by alkyl, dialkyl or hydroxy, provided that when A includes hydroxymethylene, the hydroxymethylene group is not adjacent to a heteroatom; B represents sulfur, sulfoxide, sulfone, oxygen, --NH-- or nitrogen substituted by alkyl, phenyl, benzyl, substituted phenyl or substituted benzyl; C represents methylene or methylene substituted by alkyl; R.sub.3 represents CO.sub.2 H, CO.sup.2 -alkyl or a tetrazole group; m is 0 or 1, n is 2, 3 or 4 and p is 1, 2 or 3; and the pharmaceutically acceptable salts thereof. The compounds are specific inhibitors of 5-lipoxygenase and are useful in the treatment of local and systematic inflammation, allergy and hypersensitivity reactions and other disorders in which agents formed in the 5-lipoxygenase metabolic pathway are involved.
U.S. Pat. No. 4,621,098 and its equivalent, European Patent Application Publication No. 0131221 disclose compounds of the formula ##STR3## in which Ar is phenyl or phenyl substituted by one to three of varied substituents, for example, alkyl, alkoxy, hydroxy, etc.; Q is oxygen, sulfur or an NH group; A is straight or branched chain, optionally substituted, alkylene, and R is hydrogen or straight or branched alkyl, optionally substituted by alkoxy, hydroxyl, carboxy, alkoxycarbonyl etc.; and n is 0, 1 or 2. The disclosed compounds are indicated to have anti-inflammatory and anti-allergic properties through inhibition of undefined anaphylactic and anaphylactoid reactions, although no test data are provided. The preferred compounds are stated to be those in which Q represents oxygen and n is 0 without mention of any preference among the numerous possible substituents for R or substituted phenyl as Ar. In contrast to the invention disclosed in the foregoing publication, the compounds of the present invention all have cycloalkyl at the position corresponding to A as well as having di(tertiary)-alkyl or diphenyl groups as substituents on the phenol moiety corresponding to the substituted Ar group in the above publication which, as described therein, may or may not comprise a phenol.
U.S. Pat. Nos. 4,029,812, 4,076,841 and 4,078,084 disclose compounds of the formula ##STR4## comprising 2-(3,5-di-tert -butyl-4-hydroxy-phenyl) thio carboxamides. The compounds are indicated to be useful in lowering serum cholesterol and triglyceride levels.
A series of thioethers, useful as, for example, polyfunctional antioxidants for polymers, and biologically active substances, obtained by the nucleophilic addition of thiols, including 3,5-di-tert-butyl-4-hydroxythio-phenol, and hydrogen sulfide to acrylate derivatives have been described. See Medvedev et al., Khimiya; Khimicheskaya Tekhnologiya, Volume 20, (1977), pp. 568-574. The compounds resulting from the foregoing process have the general formulas RS(CH.sub.2).sub.n X and S(CH.sub.2 CH.sub.2 X).sub.2 in which R is 3,5-di-tert-butyl-4-hydroxyphenyl and X represents, for example, --C.tbd.N, NH.sub.2, CH(OH)CH.sub.2 Cl, OH, COCl and various carboxy, carboxylate and amide functions. Compounds of formula I according to the present invention or 5-lipoxygenase activity for structurally related compounds are not disclosed.
U.S. Pat. No. 4,153,803 discloses cholesterol-lowering phenoxyalkanoic acid esters of the formula ##STR5## wherein, when Y is sulfur, X is hydrogen, benzyl, benzyloxy or benzylthio or substituted derivatives thereof; R is hydrogen halogen, hydroxy, alkyl or alkoxy, A.sup.1 and A.sup.2 are hydrogen or alkyl and Z is amine or azacyclohydrocarbonyloxy.